(Technical Field)
The present invention relates to an electric power system that includes a plurality of (three or more in particular) power converters.
(Related Art)
A known system of this type is disclosed, for example, in patent document JP-A-2010-233292. The system disclosed in this patent document includes a plurality of (N number of) power converters which are operated with the switching frequencies being synchronized and with an appropriate phase difference being given. In the system, a phase angle of approximately 2π/(N·n) is ensured to be set, where n is a minimum order of harmonic components of the switching frequencies that are approximate to a lower limit frequency in a noise standard with which the system should be compliant.
In such systems based on conventional art including the one mentioned above, the correlation between switching phases are fixedly set on the basis of solely a value similar to a constant, such as the number of converters, which does not rely on the system's operating conditions. Therefore, the systems of this type based on the conventional art are not yet sufficient at all from the viewpoint of suppressing ripple current and the noise accompanying the ripple current when there is a change in the operating conditions (i.e. in the input/output electric powers of the individual power converters).